Process for the manufacture of titanium dioxide



Patented Nov 14,1942

. UNITED STATES PATENT OFFICE PROCESS FOR THE MANiIFACTURE OF TITANIUMDIOXIDE Peter Tillmann, Cologne, Friedrich Raspe, Leverkusen-I. G. Work,and Josef Heinen, Cologne,

Germany, assignol's to Titan Company, Inc., Wilmington, Del., acorporation of Delaware No Drawing. Application November 2, 1938, Se-

rial No. 238,358. 1937 Claims.

This invention relates to a process for the manufacture of titaniumdioxide by hydrolysisof a titanium salt solution in the presence of ahydrated titanium oxide sol and tea method of pre-' tions in thepresence of a 501 formed by dilution and heat treatment of an univalentanion titani-' um solution diluted with hot water.

Many processes forthe manufacture of titanium dioxide-pigments whichconsist in decomposing a. titanium compound by heat hydrolysis areknown. It is also known to influence this hydrolysis by the addition ofany kind of nuclei in a desired direction. For this purpose titaniumdioxide gel and colloidal titanium dioxidehave been used as nuclei.These colloidal titanium dioxide sols are partly obtained by subjectinga titanium salt solution to careful heat treatment whereby sols areobtained by a condensation In Germany November 5,

process. A great advance in the'manufacture of titanium pigments wasobtained by carrying out with univalent anions which for developing thenucleating properties have been heated, for inwhite' lead.

In accordance with'the present invention it is possible to obtainexcellent pigments with sols obtained by peptization which pigments showa tinting strength which is 1819 times better'than the tinting strengthof the usual commercial I white lead.

For this purpose it is necessary that the titanium hydratesused forpeptization are practically free from polyvalent anions. Freeing of thetitanium hydrates .from the polyvalent anionsis effected in the usualmanner, for instance by neu-.

tralizing the titanium hydrate with neutralizing agents, such 'as forinstance alkali metal hydrox hydrolysis with the assistance oftitaniumsols 3 are formed the polyvalent anions can be'removed bywashing with water. According to another possibility to obtain a solwithout polyvalent an ions the treatment may be effected by adding tothe titanium hydrate an agent yielding with the polyvalent anionspresent in the titanium hy-' drate-water-insoluble compounds, forinstance I Ba(OH)2, BaClz, SrCOa or other alkaline-earth metalcompounds, eliminate the polyvalent anions present in the titaniumhydrate, for instance the SO4ion by; prolonged andrepeated washing withwater.. After the titanium hydrate has been'freed from: the polyvalentanions the peptization of the TiOz is effected with monobasic acidagents, such as for instance hydrochloric acid, nitric acid, titaniumtetrachloride. Sols the 'I'iOz-concentration of which does not exceedgrams of titanium dioxide per liter are particularly efficacious. As thelower limit practically not less than 5 grams .of 'IfiOz' per litershould be taken; The quantity of nuclei necessary for hydrolyzing agiven quan-' tity of a titanium salt solution is preferably within therange of 8'-20% calculated on the amount of TiOz present in the solutionto be hy drolyzed.

If a titanium sulfate solutionis used for pre-p parin titanium dioxideit is advantageous to fix the proportion of TiOzto sulfuric acid boundto TiOz from 1:1.to aboutj1-.8. Hydrolysis is advantageously carried outin such a manner that either the sol or the solution to be hydrolyzed orboth are heated prior to hydrolysis and caused to react one upon theother. If nitric acid is used as peptization agent for the manufactureof the sol, or other acids con- .taining nitrogen and oxygen, it isimportant to keep the usual Ti concentration which must be withsulfuric'acid so high that it'is sufiicient to reduce the acid used forpeptization of the nuclei quantitatively. This reduction is ofconsiderable ides and carbonatesor ammoniaand its compounds. Since inthis case water-soluble salts lowing examples without being restrictedthereto:

importance for avoiding corrosion of the apparatus. i

The products obtained in this manner are of excellent whiteness and showa tinting strength which is far superior to the usual commercialproducts. I 1

If the hydrolysis iscarried out in the presence of extenders or fillers,such as BaCOa, BaSO4, silica, C3304, composite pigments of excellentquality, are obtained. r

' The invention is further illustrated bythe fol- Furthermore it is'possible'to Example 1.--100 grams of titanium hydrate freshlyprecipitated from a titanium sulfate solution containing 35 grams ofT102 are suspended in 2 liters of water. The suspension thus obtained isneutralized with ammonia. By treating the suspension three times with 4liters of water and subsequent filtration the main quan- Grams T102 perliter 140 FeSOa do 180 H2304 bound to 'I'iOz do 253 Ti (10.. 2.1

The whole mixture is heated and kept boiling,

for half an hour. The yield of T102 obtained is between 96% and 98%.After the customary after-treatment and calcination a pigment isobtained which hasa tinting strength of about 1700 according to theReynold method.

Example 2.-100 grams of titanium hydrate paste according to Example 1are neutralized-with ammonia and heated with 300 cos. of 10%hydrochloric acid for several hours to 80 C. After filtering thehydrochloric acid on the suction filter enough HCl is present in theT102 to obtain a sol formation in the subsequent treatment with 1800grams of water. ccs. of the titanium sulfate solution used in thisexample according to the precipitation method indicated in Example 1yield a pigment of the same high tinting strength.' I

Example 3.-l g. of titanium hydrate paste according to Example 1 aresuspended with 400 ccs. of 10% hydrochloric acid and heated to 80- 85 C.for 5 hours. The solution is then filtered with suction and again heatedto 85 C. with 400 ccs. of hydrochloric acid for 5 hours. After filteringthe hydrochloric acid with suction as indicated in the precedingexamples a $01 formation can be observed on diluting with 1800 grams ofwater. The sol together with the titanium sulfate solution indicated inExample 1 in the proportion 1:1 likewise yields pigments of high tintingstrength.

Examples-Grams of titanium hydrate paste are neutralized and washed asindicatedin Example l'and treated with 23 ccs. of HNOa. The sol isbrought with water to a content of 19.2 grams of TiOz per liter andheated on the water bath to 90-95 C. 500 ccs. of the titanium sulfatesolution according to Example 1 are heated to boiling and 61 ccs. of atitanous sulfate solution TiOz, admixing a sufllcient amount of the re-500 ccs. of this sol and 500 sultant sol with a titanium salt solutionto yield between about 8 percent and about 20 percent of the totaltitanium calculated asjIiOz in the mixture and hydrolyzing that mixture.

2. Process for the hydrolytic decomposition of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from atitanium salt solution, purifying the precipitated titanium hydrate bymeans of an alkaline reacting neutralization agent, peptizing thepurified titanium hydrate in water by means of a peptizing agent thenegative ion of which is univalent and heating the resultant colloidalsuspension until a stabilized, slightly opalescent, unfilterable sol isformed, the proportions of water hydrate and of the peptizing agentbeing such that the resulting sol will contain between about 5 grams' toabout 50 grams of titanium per litre calculated as TiO2, admixing asuflicient amount of the resultant sol with a titanium salt solution toyield between about 8 percent and about 20 percent of the total titaniumcalculated'as TiO-z in the mixture and hydrolyzing that mixture.

3. Process for the hydrolytic decomposition of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from atitanium salt solution, purifying the precipitated titanium hydrate byneutralization with ammonia'and removing th ammonium salt formed bywashing, peptizing the purified titanium hydrate in water by means of apeptizing agent the negative ion of which is univalent and heating theresultant colloidal suspension until a stabilized, slightly opalescent,unfilterable sol is formed, the proportions of water, hydrate and of thepeptizing agent being such that the result ing sol will contain betweenabout 5 grams to about 50 grams of titanium per litre calculated asTiOz, admixin a sufiicient amount of the resultant sol with a titaniumsaltsolution to yield between about 8 percent and about 20 percent ofthe total titanium calculated as T102 in the mixture and hydrolyzingthat mixture.

4. Process for the hydrolytic decomposition of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from atitanium sulfate solution, peptizing th titanium hydrate inwater bymeans of an alkaline earth metal compound the negative ion of which isunicontaining 80 grams of Ti per liter are added.

hydrate in water by means of a peptizing agent valent and heating theresultant colloidal suspension until a stabilized, slightly opalescent,unfilterable sol is formed, the proportions of water hydrate and of thepeptizing agent being such that the resulting sol will contain betweenabout 5 grams to about 50 grams of titanium per litre calculated asT102, admixing a suflicient amount of the resultant sol with a titaniumsalt solution to yield between about 8 percent and about 20 percent ofthe total titanium calculated as TiOz in the mixture and hydrolyzingthat mixture.

5. Process for the hydrolytic decomposiion of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from atitanium salt solution, purifying the precipitated titanium hydrate,peptizing the purified titanium hydrate in water by means of amono-basic acid agent and heating the resultant. colloidal prisesprecipitating titanium' hydrate from a titanium salt solution, purifyingthe precipitated titanium hydrate, peptizing the purified titaniumhydrate in water by means of titanium tetrachloride and heating theresultant colloidal suspension until a stabilized, slightl: opalescent,un-

filterabl sol is formed, the proportions of water,

hydrate and of the peptizing agent being such that the resulting solwill contain between about 5 grams to about 50 grams of titanium perlitre calculated as '-IiO2, admixin a sufiicient amount of the resultantsol with a titanium salt solution 'to yield between about 8 percent andabout 20 percent of the total titanium calculated as TiOz in the mixtureand hydrolyzing that mixture.

'7. Process for the hydrolytic decomposition of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from .atitanium salt solution, purifying the precipitated titanium hydrate,peptizing the purified titanium hydrate in water by means of a monobasicacid and heating the resultant colloidal suspension until a stabilized,slightly opalescent, unfilterable sol is formed, the proportions ofwater, hydrate and of the peptizing agent being such'that the resultingsol will contain between about 5 grams to about 50 grams of titanium perlitre calculated as 'IiOz, admixing a sufficient amount of the resultantsol with a titanium salt solution to yield between about 8 percent andabout 20 percent of the total titanium calculated as TiOz in the mixtureand hydrolyzing that mixture.

8. Process for the hydrolytic decomposition of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from atitanium salt solution, purifying the precipitated titanium hydrate,peptizing the purified titanium hydrate in water by means of nitric acidand heating the resultant colloidal suspension until a stabilized,slightly opalescent, unfilterablesol is formed, the proportions ofwater, hydrate and of the peptizing agent being such that the resultingsol will contain between about 5 grams to about 50 grams of titanium perlitre calculated as Ti02, admixing a sufiicient amount of the resultantsol with a titanium salt solution to yield between about 8 percent andabout 20 percent of the total titanium calculated as TiOz in the mixtureand hydrolyzing that mixture.

9. Process for the hydrolytic decomposition of a hydrolyzable titaniumsalt solution which comprises precipitating titanium hydrate from atitanium salt solution, purifying the precipitated titanium hydrate,peptizing the purified titanium hydrate in water by means of nitric acidand heating the resultant colloidal suspension until a stabilized,slightly opalescent, unfilterable sol is formed the pro-portions ofwater, hydrate and of the peptizing agent being such. that the resultingsol will contain between about 5 grams to about 50 grams of titanium perlitre calculated as TiOz, admixing a sufiicient amount of the resultantsol with atitanium salt solution to yield between about 8 percentandabout 20 percentof the total titanium calculated as T102 in the mixtureand hydro-lyzing that mixture, said hydro lyzable titanium salt solutioncontaining an amount of 'Ii at least sufiicient' for the reduction ofthe nitric acid.

10. Process for the hydrolytic decomposition of l a hydrolyzabletitanium salt solution which comprises-precipitatin titanium hydratefrom a titanium salt solution, purifying the precipitated titaniumhydrate, peptizing the purified titanium hydrate in water by means ofhydrochloric acid V and heating the resultant colloidal suspension untila stabilized, slightly opalescent, unfilterable sol is formed, theproportions of water, hydrate and of the peptizing agent being such thatthe resulting sol will contain between about 5 grams to about 50 gramsof titanium per litre calcu-.

lated as TiOz, admixing a sufficient amount of the resultant sol with atitanium salt solution to yield the total titanium calculated as TiOz inthe mixture and hydrolyzing that mixture.

PETER TILLMANNQ FRIEDRICH RASPE. JOSEF HEINEN.

